An apparatus of the kind described in the opening part of this specification is known from DE 35 45 080 C2. In that arrangement the yarn guide is guided with a component of movement which can be generally referred to as a creep motion or edge control, thereby counteracting a build-up of the package in the edge regions. This also counteracts the formation of an image-type winding or a mirror-type formation at the periphery of the package. This is achieved by a reversing screwthread drum and a yarn guide, as well as by a control arrangement connected thereto for actuating the traversing yarn guide with a creep stroke motion. The reversing screwthread drum has an endless screwthread groove which guides the yarn to and fro a plurality of times so that a plurality of reversals are formed on each side of the reversing screwthread shaft. Those reversals are arranged in a mutually displaced relationship. No information is provided about the nature of the pitch or gradient of the screwthread groove. The illustration of an embodiment in the drawing shows a constant pitch or gradient. An embodiment of a reversing screwthread shaft is illustrated, in which the first double stroke has the turns number 7.4 and the second double stroke has the turns number 7.6. The integral component is thus greater than 2 and the balance represents a true fraction. Half the turns number which establishes a forward stroke of a double stroke and half the turns number which establishes the associated reverse stroke are respectively different. The control arrangement required for implementing the creep motion of the yarn guide signifies additional expenditure.
German laid-open applications (DE-OS) Nos. 21 18 217 20 27 005 disclose groove drums in which (FIGS. 1-3) a respective revolution of the groove drum produces the entire procedure of the program. With these embodiments, two double strokes or periods are produced for each groove drum. In the embodiments in FIG. 3, there are three double strokes per revolution. FIGS. 4 and 6 of DE-OS No. 20 27 005 show two embodiments in which the groove in the groove drum is of such a shape and arrangement that, for example, two periods are distributed over three revolutions of the groove drum. This arrangement therefore involves a true fraction as the relationship. FIGS. 5 and 7 of this publication also show two further embodiments in which the reversed relationship is used. Here, three periods are distributed over two revolutions and four periods over three revolutions, respectively, so that the relationship involves a mixed number whose integral component is equal to 1 and whose balance represents a true fraction. The pitch or gradient of the groove in the groove drum is substantially constant. Specific and deliberate shaping in the region of the reversals in the form of curve lines is intended to alleviate the edge build-up effect and to enhance the strength of the package.
The object of the invention is to provide an apparatus of the kind set forth in the opening part of this specification, that is to say an apparatus having a reversing screwthread shaft, in which image windings are reliably avoided, without additional control arrangements being required. In particular, the invention seeks to provide that this is possible in the case of a yarn guide with a creep stroke motion, that is to say the sweep or wobble effect is not to impede the production of a creep stroke motion.